Extending the age limit of quartz OSL dating of Chinese loess using a new multiple-aliquot regenerative-dose (MAR) protocol with carefully selected preheat conditions

Abstract

Abstract Optically Stimulated Luminescence (OSL) dating on quartz is well established following the introduction of the Single-Aliquot Regenerative-dose (SAR) protocol. Despite its widespread use, it has a major drawback in frequently underestimating the age of samples with equivalent dose (De) larger than ~120 Gy. In this study, we investigate fine-grained quartz extracted from Chinese loess with fairly well known ages. For these samples, we determined that the Des obtained using the standard SAR protocol (i.e., with preheat and cut-heat temperatures of 260 °C and 220 °C respectively) significantly underestimated the expected burial doses larger than 100 Gy. The dependence of OSL intensity on preheating conditions was investigated using both natural and bleached aliquots. Both the natural and regenerative OSL intensities increase with the preheat temperature to a maximum at ~260 °C and decrease afterwards. However, the regenerated OSL intensity demonstrates a greater variability compared to the natural one. This difference in variability could not be corrected by the test dose OSL responses when a standard SAR protocol was used. A simple multiple-aliquot regenerative-dose (MAR) protocol with a carefully selected preheating condition can resolve the problem of inadequate sensitivity correction between the natural and subsequent regenerative cycles. The growth of the MAR dose-response curve (DRC) was in good agreement with the sensitivity-corrected natural OSL signals up to ~340 Gy, which extends the upper age limit of quartz OSL samples of Chinese loess back to at least 110 ka.